Abstract:Thiobacillus thermophilus(moderate thermophile) was used to leach low-grade phosphate ore.The bacteria that can resistant to high slurry concentrations was obtained by step-by-step transfer of domestication.The differences of microbial morphology, ore composition, domesticated strains and domesticated leaching were studied. The leaching efficiency was improved by adding surfactants and carbon sources, and the leaching mechanism of microorganisms in the leaching process was characterized in different ways.A phosphate mine with a grade of 13.17 %, microorganisms are short rod-shaped (500-650)×(150-250) nm .The activity of the domesticated strain was significantly higher than that of the undomesticated strain. The leaching of the domesticated strain tended to be stable at 11 d, and the final phosphorus leaching rate was 81.3%, which was 9.8% higher than that of the undomesticated strain.The optimum dosage of Tween 20,60and 80 were10g/m3,10g/m3 and 100g/m3, respectively, and the phosphorus leaching rates were 82.88%,86.78%and 84.65%, respectively.The maximum redox potentials of glucose, starch and sucrose were 482 mV, 414 mV and 438 mV, respectively, and the leaching rates were 80.2%, 83.9% and 86.8%, respectively.After the action of microorganisms, the surface of phosphate rock becomes rough, uneven, with material accumulation, and erosion pits can be observed on the surface ; most of the thermophilic acid-sulfur bacilli are adsorbed on the cracks and defects of phosphate rock particles ; the infrared spectrum analysis proved that there was indeed the adsorption of thermophilic acid-sulfur bacillus on the surface of phosphate minerals.The Zeta potential test of phosphate rock showed that the isoelectric points of phosphate rock and thiobacillus thermophilus were pH 4.5 and pH 2.8, respectively. The contact angle of phosphate rock in deionized water is 43.7°, and the contact angle in sulfuric acid with pH of 2.8 was 44.9°.After the action of microorganisms, the wetting contact angle of phosphate rock surface was 68.5°, and the hydrophobicity was obviously enhanced.